The present invention relates to decompression panels for use in a separation structure, such as a bulkhead or wall, and more particularly, to decompression panels having a pressure relief panel that releases entirely from the device during rapid decompression of a pressurized compartment.
An aircraft is typically subdivided into two or more compartments separated by structures, e.g., walls, bulkheads, floors, etc. During flight, these compartments are positively pressurized relative to the atmospheric pressure outside the aircraft. If an opening is created between one compartment and the exterior atmosphere, the pressure difference causes a sudden exodus of interior aircraft air. As air is rushing out the opening, an almost immediate propagation of the pressure difference causes the other compartments to also attempt to decompress.
To accommodate this chain reaction of pressure differences, it is often necessary to provide decompression panels between compartments to quickly equalize the pressure differential. A difference in pressure between compartments that is not relieved rapidly could lead to deformation of a separation structure and/or surrounding components. Known decompression panels have a sandwich type construction in which a pressure relief panel is released to fully reveal an opening through the separation structure. This allows air to quickly pass therethrough and quickly relieve the pressure difference. These types of decompression panels are sometimes referred to as full release blowout panels.
There are other aircraft requirements, however, that must be considered along with the requirement to allow air to pass between compartments during decompression. In particular, some aircraft compartments rely on oxygen suffocation to extinguish fires. This requires the separation structures to act as oxygen-tight fire barriers that do not allow fire or oxygen to pass through them. In such cases, it would be advantageous to use a pressure relief panel that could quickly allow pressure equalization between compartments during a rapid decompression event, but would otherwise resist the spread of fire between compartments. This present invention is directed to providing such a panel.
The present invention provides a fire-resistant decompression panel assembly for use at a separation structure to quickly relieve pressure differences between two adjacent aircraft compartments. A decompression panel assembly formed in accordance with the present invention includes a support pan or support pan having a first surface, an opening, and a raised portion (e.g., a bull nose) surrounding the periphery of the opening and extending normally outward from the first surface. A pressure relief panel is used to cover the support pan opening and is therefore sized slightly larger than the opening. A retaining ring connects to the support pan such that the outer edge of the pressure relief panel is located and held between the raised portion and the retaining ring.
The retaining ring includes a number of segments or fingers available to flex independently of one another. In one embodiment of a panel assembly formed in accordance with aspects of this invention, the retaining ring is a single rectangular member having fingers formed from a number of spaced-apart slits extending into the retaining ring along the ring""s inner periphery. Stress relief holes are provided at the ends of the slits to prevent crack growth initiation.
During normal (non-decompression) use, the fire resistant pressure relief panel is clamped between the retaining ring and the raised portion. The contacts between the ring, the pressure relief panel, and the raised portion are substantially airtight contacts, so that the panel assembly can prohibit the flow of oxygen and smoke between compartments and thereby resist the spread of fire and smoke. During a decompression event, one or more of the retaining ring fingers flexes slightly outward and in so doing reduces the holding force applied to the fire resistant pressure relief panel. This allows the pressure difference between compartments to easily and quickly detach the entire panel from the assembly.
In accordance with further aspects of this invention, the pressure relief panel is made of a fire resistant fiberglass and the retaining ring is fabricated from nickel chromium stainless steel. The panel assembly is preferably oriented in an upright plane with the support pan opening, pressure relief panel, and retaining ring rectangular shaped and oriented with their longitudinal axes extending laterally.
In accordance with other aspects of this invention, there are a number of optional features that may be included to enhance particular aspects of the panel""s performance. To help centrally align the pressure relief panel during assembly, a number of index pins interconnect between the support pan and the retaining ring. In particular, the index pins extend from the support pan first surface and protrude through clearance holes provided in the retaining ring. The index pins are located such that the pressure relief panel edges just contact the pins. The pins therefore act as stop guides. The support pan may further include a recess surrounding the raised portion. An inner seal is sized and located within the recess, and is pocketed between the support pan and the retaining ring during use. The inner seal acts as an ablating heat sink.
The panel assembly may also include a grill for use in protecting the fire resistant pressure relief panel from objects within the compartment. In one embodiment, the support pan includes a second surface having a peripheral flange extending normally therefrom about the pan opening. A number of secondary pressure relief holes extend through both the grill sides and the flange to provide relief pressure equalization should the face of the grill be blocked. The grill is attached to the flange and generally covers the entire support pan opening. The grill is preferably formed by machining or casting a heat tolerant material, such as aluminum, titanium, cobalt, steel, etc.
In another embodiment, the panel assembly includes a deflection plate attached to the outlet side of the assembly that deflects the pressure relief panel and the airflow through the panel. This embodiment helps protect equipment or other items from damage caused by the impact of the panel or by the pressure from the air stream flowing through the panel opening.
In another embodiment, the panel assembly has an air inlet with curved edges that improves the airflow through the panel and, if made of a fire-resistant material, also improves the fire-resistant characteristics of the assembly.
In another embodiment, the panel assembly has a shaped grill on the inlet side of the assembly. This embodiment helps prevent blockage of the air passageway of the panel by luggage, cargo, or other objects.
These and other advantages of the invention will be apparent from the description that follows.